An Optical Transport Network (OTN) is comprised of a plurality of switch nodes linked together to form a network. The OTN includes an electronic layer and an optical layer. The electronic layer and the optical layer each contain multiple sub-layers. The optical layer provides optical connections, also referred to as optical channels or lightpaths, to other layers, such as the electronic layer. The optical layer performs multiple functions, such as monitoring network performance, multiplexing wavelengths, and switching and routing wavelengths. In general, the OTN is a combination of the benefits of SONET/SDH technology and dense wavelength-division multiplexing (DWDM) technology (optics). OTN structure, architecture, and modeling are further described in the International Telecommunication Union recommendations, including ITU-T G.709, ITU-T G.872, and ITU-T G.805, which are well known in the art.
The construction and operation of switch nodes (also referred to as “nodes”) in the OTN is well known in the art. In general, the nodes of an OTN are generally provided with a control module, input interface(s) and output interface(s). The control modules of the nodes in the OTN function together to aid in the control and management of the OTN. The control modules can run a variety of protocols for conducting the control and management of the OTN. One prominent protocol is referred to in the art as Generalized Multiprotocol Label Switching (GMPLS).
Generalized Multiprotocol Label Switching (GMPLS) is a type of protocol which extends multiprotocol label switching (MLS) to encompass network schemes based upon time-division multiplexing (e.g. SONET/SDH, PDH, G.709), wavelength multiplexing, and spatial switching (e.g. incoming port or fiber to outgoing port or fiber). Multiplexing is when two or more signals or bit streams are transferred over a common channel. Wave-division multiplexing is a type of multiplexing in which two or more optical carrier signals are multiplexed onto a single optical fiber by using different wavelengths (that is, colors) of laser light.
RSVP and RSVP-TE signaling protocols may be used with GMPLS. To set up a connection in an Optical Transport Network, nodes in the Optical Transport Network exchange messages with other nodes in the Optical Transport Network using RSVP or RSVP-TE signaling protocols. Resources required for the connection are reserved and switches inside the network are set. Information sent by signaling protocols are often in a type-length-value (TLV) format. The same protocols may also be used to take down connections in the Optical Transport Network when the connections are no longer needed.
OSPF and OSPF-TE routing and topology management protocols may also be used with GMPLS. Under OSPF protocols, typically each node in an Optical Transport Network maintains a database of the network topology and the current set of resources available, as well as the resources used to support traffic. In the event of any changes in the network, or simply periodically, the node floods the updated topology information to all the Optical Transport Network nodes. The nodes 20 use the database information to chart routes through the Optical Transport Network.
Traffic Engineering (TE) is a technology that is concerned with performance optimization of operational networks, such as OTNs. In general, Traffic Engineering includes a set of applications, mechanisms, tools, and scientific principles that allow for measuring, modeling, characterizing and control of user data traffic in order to achieve specific performance objectives.
Current Traffic Engineering practices have been utilized to increase the data rates in networks. However, future information transport systems are expected to support service upgrades to data rates of one terabyte per second (Tbps) and beyond. To accommodate such high rates in transport network architectures, multi-carrier Super-Channels coupled with advanced multi-level modulation formats and flexible channel spectrum bandwidth allocation schemes may be utilized. Conventional wavelength switched optical networks are based on a fixed ITU-T DWDM wavelength frequency grid. A frequency grid is a reference set of frequencies used to denote allowed nominal central frequencies that may be used for defining applications. Historically, the frequency grid defined by the ITU-T G.694.1 recommendations supported a variety of fixed channel spacings ranging from 12.5 GHz to 100 GHz and wider (integer multiples of 100 GHz). Uneven channel spacings within the fixed grid were also allowed.
The fixed grid-based approach does not seem adapted to new data rates beyond 100 Gbps, and it is particularly inefficient when a whole wavelength is assigned to a lower speed optical path (e.g., 10 Gb/s) that does not fill the entire wavelength capacity. To enable scaling of existing transport systems to ultrahigh data rates of 1 Tb per second and beyond, next-generation systems providing super channel switching capability are currently being developed. To allow efficient allocation of optical spectral bandwidth for such high bit rate systems, International Telecommunication Union Telecommunication Standardization Sector (ITU-T) is extending the G.694.1 grid standard (termed “fixed-grid”) to include a flexible grid support.
In particular, the recent revision of ITU-T Recommendation [G.694.1] has decided to introduce the flexible grid DWDM technique which provides a new tool that operators can implement to provide a higher degree of network optimization than fixed grid systems. The flexible grid DWDM technique provides a plurality of spectral slices within the frequency grid that can be arbitrarily assigned or aggregated to provide frequency slots having one or more spectral slices. Further, frequency slots can be defined having different amounts of spectral slices to provide the frequency slots with different widths. This means in such networks that an adjacent channel spacing and assigned spectral bandwidth per wavelength are variable to form a mixed bitrate transmission system. Mixed bitrate transmission systems can allocate their channels with different spectral bandwidths so that they can be optimized for the bandwidth requirements of the particular bit rate and modulation scheme of the individual channels.
This technique is regarded as a promising way to improve the network utilization efficiency and to fundamentally reduce the cost of the core network. Based on the DWDM technique, Wavelength Switched Optical Network (WSON) uses a control plane of the switch node to dynamically provide Label Switched Paths (LSPs) for the requested end to end connections. The label switching is performed selectively on wavelength labels representing the center wavelength/frequency of the frequency slot.
However, there is not currently a method or system for the nodes within the optical network to effectively advertise unreserved bandwidth within the optical network using the flexible grid system resulting in underutilization of the resources within the optical network. What is needed are techniques in which nodes within an optical network can advertise available bandwidth that can be used to set up variable bandwidth connections using the techniques defined, for example, in ITU-T G.694.1. Techniques for advertising available bandwidth in an optical network using the flexible grid systems are disclosed herein.